Turbomachine blade

Abstract

A turbomachine blade includes a root intended to be mounted in a recessed pocket of a turbomachine rotor disc, the root having two side faces extending radially and longitudinally, each of the side faces including at least one seating intended to be inserted against a side wall of the recessed pocket, along an axis of longitudinal direction and to be in contact with the side walls of the recessed pocket, a radially inner face intended to face the bottom of the recessed pocket when the root is mounted in the recessed pocket, the radially inner face connecting the two side faces, the radially inner face including at least one curved concave surface and two curved convex surfaces, the curved concave surface extending from one end of each of the two curved convex surfaces.

Claims

1. A turbomachine blade comprising a root adapted to be mounted in a recessed pocket of a turbomachine rotor disc while extending radially vis-à-vis a longitudinal axis, the root having: a. two side faces extending radially and axially, each of the two side faces including at least one seating to be in contact against a wall of the recessed pocket, along the longitudinal axis, b. a radially inner face to face the bottom of the recessed pocket when the root is mounted in the recessed pocket, the radially inner face connecting the two side faces, the radially inner face comprising an undulation including at least one first rounded surface, a second rounded surface and a third rounded surface, the second rounded surface extending from one end of each of the first and third rounded surfaces, the first and third surface being separate from each other and wherein: i. the first rounded surface and the third rounded surface are concave, and the second rounded surface is convex, ii. or the first rounded surface and the third rounded surface are convex and the second rounded surface is concave, and wherein the radially inner face includes a plurality of undulations formed by an alternation of concave and convex surfaces along the longitudinal axis to avoid having a sharp edge between the alternation of concave and convex surfaces.

2. The turbomachine blade according to claim 1, wherein the rounded concave and convex surfaces undulate along the longitudinal axis from an upstream face of the root to a downstream face of the root.

3. The turbomachine blade according to claim 2, wherein the concave and convex surfaces are aligned along the longitudinal axis.

4. The turbomachine blade according to claim 3, wherein each rounded concave or convex surface extends into a median region of the radially inner surface of the root, the median region being situated at a distance from the two side faces of the blade root.

5. The turbomachine blade according to claim 1, wherein the rounded concave and convex surfaces undulate in the transversal direction while connecting together the two side faces.

6. An assembly of at least one turbomachine blade according to claim 1 and a turbomachine rotor disc mounted around the longitudinal axis and including, on a periphery thereof, a plurality of recessed pockets regularly distributed around the longitudinal axis, the root of said at least one blade being mounted in a recessed pocket of the plurality of recessed pockets so as to form a mounting clearance between the root of the blade and the bottom of said recessed pocket.

7. The assembly according to claim 6 wherein the recessed pocket includes cooling channels which emerge radially in the bottom of said recessed pocket and inter-cavity partitions that separate the cooling channels and wherein the convex surfaces of the root of the blade are laid out in line with the inter-cavity partitions.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The figures are presented for indicative purposes and in no way limit the invention.

(2) FIG. 1 partially represents, in exploded view and schematically, a turbomachine rotor disc and a blade root according to a first example of a first embodiment of the invention.

(3) FIG. 2 partially represents, schematically in section, a turbomachine rotor disc and a blade root according to a second example of the first embodiment of the invention.

(4) FIG. 3 schematically represents a section of blade root according to a second embodiment of the invention.

(5) FIGS. 4a and 4b each represent a perspective of a third embodiment of blade root according to the invention.

(6) FIG. 5 partially represents a recessed pocket of a rotor disc including cooling channels.

DETAILED DESCRIPTION

(7) Unless stated otherwise, a same element appearing in the different figures has a single reference.

(8) FIG. 1 represents partially, in exploded view and in a schematic manner, a first example of root 16 of the blade 14 according to a first embodiment of the invention and partially an example of turbomachine rotor disc 2. FIG. 2 schematically shows a radial section of a root 16′ according to a second example of this embodiment in a recessed pocket of a second example of disc 2′.

(9) The disc 2, extends around an axis of rotation A, comprises on its periphery a plurality of recessed pockets 4 open towards the exterior of the disc 2 and regularly distributed angularly around the axis of rotation A of the disc 2.

(10) The blade 14 has an extension dimension along a first direction or radial direction y and is intended to be mounted in a recessed pocket 4 of the disc 2 in rotation around an axial direction A or axis of rotation A. The blade 14 includes a root 16 mounted in the recessed pocket 4 of the disc 2, so as to form a blade-disc link. At each point of the blade 14 are defined: the first radial direction y along the extension dimension of the blade 14, a second axial direction x, perpendicular to the radial direction and parallel to the axis of rotation A, and a third direction or tangential direction z, perpendicular to the radial direction y and to the axial direction x.

(11) In particular, when the blade 14 is mounted in a recessed pocket 4 of the disc 2: the radial direction y is along a radius of the disc 2 or in other words perpendicular to the axis of rotation A of the disc 2; the axial direction x is parallel to the axis of rotation A of the disc 2 and the tangential direction z is both perpendicular to the radial direction y and perpendicular to the axial direction x.

(12) Hereafter, the axial direction x is also designated the longitudinal axis x of the blade root, which is thus parallel to the axis of rotation A.

(13) The root 16 includes a radially inner face 3 and the recessed pocket 4 includes a bottom 41 facing the radially inner face 3.

(14) The radially inner face 3 is opposite the radial direction, the face of the root 16 the closest to the axis of rotation A.

(15) The root 16 also includes at its radially outer end, radially opposite to the radially inner face of the root, a platform from which a vane extends radially outwards.

(16) The root 16 and the recessed pocket 4 are dimensioned so as to arrange, when the root 16 is mounted in the recessed pocket 4, a space or mounting clearance between the bottom 41 and the radially inner face 3 of the root 16, in which cooling air can circulate.

(17) The root 16 comprises a first side face 6a and a second side face 6b extending in the axial direction x and in the radial direction y. In particular, the side face 6a and the side face 6b form a dovetail root 16. The root 16 further includes an upstream face 7 and a downstream face extending in the tangential direction Z and in the radial direction y.

(18) The radially inner face 3 is delimited longitudinally on either side by the upstream face 7 and the downstream face and transversally, in other words over its width, on either side by the side face 6a and the side face 6b.

(19) The radially inner face 3 thus extends in the axial x and tangential Z direction.

(20) In particular, on an upstream face 7 of the root 16 may be seen the dovetail shape. The recessed pocket 4 includes two side walls 4a, 4b, of shape complementary to the side faces 6a, 6b of the root 16. In particular, each side wall 4a, 4b includes in this first example a portion of radially outer wall 42a having a curved convex surface and a portion of radially outer wall 42b having a curved concave surface. Each side wall 4a, 4b is in contact respectively with the side faces 6a, 6b of the root 16 of the blade 14.

(21) In this example, each of the two curved side faces 6a, 6b comprises a concave surface each including radiuses forming a radially outer seating 61 and a radially inner seating 62. Each seating surface 61, 62 is in contact with a side wall of the recessed pocket 4, along an axis of longitudinal direction Y, which in this example is parallel to the axis of rotation A.

(22) FIG. 2 schematically shows a second example of root 16′ of the blade 14 according to an embodiment of the invention. The root 16′ according to the second example comprises a first and a second side face 6a′, 6b′ different from those of the first example in that each of these two side faces 6a′, 6b′ further comprises a convex surface in the radially outer part of the side face whereas the root 16 according to the first example does not comprise one.

(23) The root 16′ comprises on each of these two side faces 6a′, 6b′, a radially outer seating 61 formed by the convex surface, an intermediate seating 63 formed by the concave and convex surface, and a radially inner seating 62 formed by the concave surface.

(24) In this second example, each side wall 4a′, 4b′ (referenced in FIG. 5 and described in detail hereafter) of the recessed pocket 4′ comprises a portion of radially inner side wall and a portion of radially outer side wall. The radially outer seating 61 is in contact with the portion of radially outer side wall. The radially inner seating 62 and the intermediate seating 63 are in contact with the portion of radially inner wall. Each portion of radially inner wall includes a curved convex surface 463 visible notably in FIG. 5 detailed hereafter representing a radial view of the recessed pocket 4′ of the disc 2′. Each portion of radially outer wall includes a curved concave surface and a free curved convex surface.

(25) The intermediate seating 63 is thus in contact with the convex surface 463 of the portion of radially inner wall.

(26) Side mounting clearances between the root 16′ and the side walls 4a′, 4b′ of the recessed pocket 4′ are formed on the one hand between the radially outer seating 61 and the intermediate seating 63 and on the other hand between the intermediate seating 63 and the radially inner seating 62. In other words, a side mounting clearance is formed between the convex surface of each side face 6a′, 6b′ of the root 16′ and the curved concave surface of the portion of radially outer wall of each side wall 4a′, 4b′ of the recessed pocket 4′. Another mounting clearance is formed between the concave surface of each of the side faces 6a′, 6b′ of the root 16′ and the curved convex surface 463 of the portion of radially inner wall of each side wall 42a, 42b.

(27) The root 16′ according to the second example is furthermore analogous to the root 16 according to the first example. In particular, the radially inner face 3 of the two examples of this embodiment is identical.

(28) FIG. 2 represents a radial section of the radially inner face 3 according to this first embodiment.

(29) A second embodiment of another root 16b is represented in FIG. 3, along an axial section of the root 16b, and is identical to the root 16′ except in that it includes a radially inner face 3b different from the radially inner face 3. A third embodiment of a root 16c is represented in perspective in FIGS. 4a and 4b, and is identical to the root 16′ except in that it includes a radially inner face 3c different from the radially inner face 3′.

(30) The common characteristics of the three embodiments will now be described and the characteristics of each of the different embodiments, in particular the different shapes of the radially inner faces 3, 3b, 3c, are described hereafter.

(31) In these three embodiments, the radially inner face 3, 3b, 3c has a width dimension along the tangential direction Z and a length dimension along the axial direction x greater than the width dimension along the tangential direction z. The width and length dimensions are each along a distinct direction and perpendicular to the radial direction y.

(32) The radially inner face 3, 3a, 3b of each embodiment includes at least one curved concave surface 31, 31b, 31c and at least two curved convex surfaces 32, 32b, 32c. In each of the embodiments, the curved concave surface 31, 31b, 31c extending from one end of each of the curved convex surfaces 32, 32b, 32c.

(33) In the first embodiment represented in FIGS. 1 and 2, the channel face 3 includes curved concave surfaces 31 and curved convex surfaces 32 in such a way that the radially inner face 3 undulates transversally with respect to the side faces 6a, 6b. The curved concave surfaces 31 and the curved convex surfaces 32 are each called hereafter respectively concave surface 31 and convex surface 32. In this case in this example, the concave surfaces 31 and the convex surfaces 32 undulate in the transversal direction while connecting together the two side faces 6a, 6b.

(34) In other words, in this first embodiment, the radially inner face 3 undulates along the tangential direction 7. In this case, the channel face 3 includes two concave surfaces 31 each including a concave radius R3, R5 extending along the transversal direction and three convex surfaces 32.

(35) “Concave radius” is taken to mean a fillet shape, while “convex radius” is taken to mean a rounded shape and “radius” is taken to mean the distance between a centre and an arc of circle.

(36) In the two examples of the first embodiment represented in FIGS. 1 and 2, each section of concave or convex surface includes a portion of a cylinder including an axis along the longitudinal direction but could very well be irregular over the length or the width while having a radius value which varies longitudinally or transversally and have a portion of an ovoid for example. However, the shape of longitudinally regular cylinder portion makes it possible to facilitate the machining or the moulding of the curved surface, whether it is concave or convex.

(37) One of the three convex surfaces 32 is a central convex surface 32″ extending between the two concave surfaces 31. The two other convex surfaces 32, hereafter called side convex surfaces 32′, are each situated on each side, along the width, of the radially inner face 3. The two side convex surfaces 32′ each extend from a radially inner seating 62 of each side face 6a, 6b. These two side convex surfaces 32′ each include in this case two convex radiuses R1, R2 and R7, R6 extending along the transversal direction. On each side, the first convex radius R1, R7 is rounded tangentially to the radially inner seating 62 and includes a smaller radius than the convex radius R2, R6 joining the concave radius R3, R5. In other words, in this example, the two side convex surfaces 32′ each include two portions of cylinder having a different radius value and a different axis parallel to the axis of axial direction x.

(38) The central convex surface 32′ only includes a single convex radius R4 along the transversal direction joining the two concave radiuses R3, R5.

(39) It will be appreciated that the third convex surface could very well have one or two or more convex radiuses and the two concave surfaces could also have two or more concave radiuses.

(40) The convex 32 and concave 31 surfaces of the radially inner face 3 are tangential to each other.

(41) Thus, this makes it possible not to form a sharp edge which can undergo more stress and thus faster wear of the root.

(42) Notably, the convex radiuses R2, R6 of the side convex surfaces 32′ with the concave radiuses R3 R5 of the concave surfaces are sufficiently large so that the change of direction enables the surfaces to extend from each other in a continuous manner.

(43) FIG. 5 represents a radial view of the recessed pocket 4′ of this second example of this embodiment. As described previously, in this FIG. 5, the convex surface 463 of the recessed pocket 4′ may be seen.

(44) The recessed pocket 4′ includes in this second example cooling channels 43 emerging radially in the bottom 41 and which are aligned following one another along the axial direction x forming between them inter-cavity partitions 44 including an axial surface forming the bottom 41. Each inter-cavity partition 44 separates two cooling channels.

(45) Each cooling channel emerges along the width, that is to say the tangential direction Z, in a median region of the bottom 41. Thus, in this example of this embodiment, the central convex surface 32″ is laid out in line with each cooling channel outlet and each inter-cavity partition.

(46) It is in this median region that the root 16′ undergoes the most stresses and thus the convex shape makes it possible to improve the wear resistance of the root 16′ in this region.

(47) Moreover, in this first embodiment, the root 16 of the first example or the root 16′ of the second example includes a radial thickness e between the radially inner face 3 and a plane P1 extending along the axial direction x and the tangential direction Z passing through a first width end called p6a and a second width end p6b of the radially inner face 3. More specifically, the first transversal end p6a is formed between the intersection of the radially inner seating 62 of the first side face 6a′ and the convex radius R1 and the transversal end p6b is formed between the intersection of the radially inner seating 62 of the side face 6a′ and the convex radius R1. The radial thickness e is thus zero at the two width ends p6a and p6b.

(48) According to another example, not represented, the plane p1 further passes through an upstream longitudinal end and a downstream longitudinal end of the radially inner face 3.

(49) The radial thickness e is thus measured along the radial direction y and varies transversally, that is to say along the width of the root, which is the tangential direction Z.

(50) In this example of this embodiment, the radial thickness e increases continually from the width end p6a to the top of the central convex surface 32″ and increases continually from the width end p6b to the top of the central convex surface 32″. The radial thickness e is thus the greatest at the level of the top of the central convex surface 32″.

(51) The curved concave surfaces 31 each have a concave radius such that the radial thickness e increases progressively towards the central convex surface 32′.

(52) The centre of each concave radius R3, R5 is thus sufficiently shifted towards the side ends so that the tangents of the concave surfaces 31 are inclined such that they form an angle with the plane P1 on the side of the corresponding longitudinal end.

(53) According to another example, not represented, the radial thickness e decreases in the concave surfaces.

(54) According to this first embodiment, the radially inner face 3 may further comprise curved concave and convex surfaces which undulate along the longitudinal direction. In this case, the section of FIG. 2 is situated either in a top of a convex surface which undulates along the longitudinal direction, or in a regular longitudinal part (of which the thickness e does not undulate along the longitudinal axis). In the case of a regular longitudinal part, the radially inner face 3 may include curved concave and convex surfaces which extend between the regular part and an upstream or downstream longitudinal end.

(55) According to a second embodiment of the invention, of which an example of a section along the longitudinal axis x of a root 16b is represented in FIG. 3, the root 16b is identical to the root 16′ of the first embodiment, except in that the radially inner face 3b is different in that the curved concave and convex surfaces undulate uniquely along the longitudinal direction. In this example, the concave and convex surfaces are curved along the axis of axial direction x and not along the tangential axis Z as in the first embodiment.

(56) The radially inner face 3b of the root of the blade has a length which extends between a first longitudinal end P7 forming the intersection line with the upstream face 7 and a second longitudinal end P8 forming the intersection line with a downstream face 8.

(57) In this example, the concave surface 31b and the convex surface 32b undulate in the longitudinal direction and connect together the upstream face to the downstream face.

(58) In this example, the radially inner face 3b includes five curved convex surfaces 32b. One of the five curved convex surfaces 32b, hereafter called upstream convex surface 32b7, extends from the first longitudinal end P7 and another of the five curved convex surfaces 32b, hereafter called downstream convex surface 32b8, extends from the second longitudinal end P8.

(59) One of the three other curved convex surfaces 32b is hereafter called central convex surface 32b′ and is situated along the longitudinal axis x between the two other curved convex surfaces 32b hereafter called curved intermediate surface 32b″. Each curved convex surface 32b and each curved concave surface 31b extends over the whole width of the radially inner face 3b.

(60) The radially inner face 3b includes four curved concave surfaces 31b each connected to two curved convex surfaces 32b in a continuous manner.

(61) A plane P1′ in this example of this second embodiment passes through the first longitudinal end P7 and the second longitudinal end P8.

(62) According to another example, not represented, the plane P1′ may also further pass through the first and second transversal ends of the radially inner face 3c.

(63) In this represented example of this second embodiment, the radial thickness e of the root measured between the plane P1′ and the radially inner face 3b varies in a sinusoidal manner while increasing in the convex surfaces and while decreasing in the concave surfaces.

(64) This example of root 16b of this second embodiment is also suited to be housed in the recessed pocket 4′ represented in FIG. 5.

(65) When the root 16b is mounted in the recessed pocket 4′, the two intermediate convex surfaces 32b″ and the central curved convex surface 32b′ are each laid out in line with an inter-cavity partition 44 of the bottom 41.

(66) The root 16b undergoes the most stresses in the convex surfaces 32b′ and 32b and thus makes it possible to improve the wear resistance of the root 16′ in this region.

(67) In this example of this second embodiment, the two intermediate convex surfaces 32b″ and the central convex surface 32b′ each include three convex radiuses R3, R4, R5, R11, R12, R13 and R7, R8, R9 extending along the longitudinal direction, in this case along the axial direction. The concave surfaces 31b each include only a single concave radius R2, R6, R10 and R14 extends in the longitudinal direction, in this case in the axial direction x.

(68) Two of the three convex radiuses of an intermediate convex 32b″ or central 32b surface are each called side convex radius R3, R5, R11, R13 or R7, R9 and extend between the concave surfaces and the other convex radius of the intermediate 32b″ or central 32b convex surface, each called central convex radius R4, R8, R12. Each side convex radius R3, R5, R11, R13 or R7, R9 has a radius value sufficiently large to be continuous with the concave radiuses R2, R6, R10 and R14 of the concave surfaces 31b. In other words, the convex radiuses R3, R5, R11, R13 or R7, R9 are rounded tangentially with the concave radiuses. The central convex radiuses R4, R8, R12 have smaller radiuses each including the tops of the intermediate 32b″ or central 32b convex surfaces. Thus, the side convex radiuses R3, R5, R11, R13 or R7, R9 are connected in a tangential manner with respectively the concave radiuses R2, R6, R10 and R14 as well as with the central convex radiuses R4, R8, R12.

(69) In this example, the upstream convex surface 32b7 and the downstream convex surface 32b8 each include respectively a convex radius R1 and R15 connected in a tangential manner with respectively the concave radiuses R2 and R14.

(70) According to a third embodiment represented in FIGS. 4a and 4b, the blade is identical except in that the root 16c includes a radially inner face 3c different from the radially inner faces 3, 3b of the two other embodiments.

(71) In this third embodiment, the radially inner face 3c comprises an undulated region represented in dashed lines including undulated convex surfaces 32c including convex radiuses along the longitudinal direction and convex radiuses in the transversal direction, that is to say the tangential direction Z.

(72) In this example of this third embodiment, the root 16c comprises hollows 161 and bosses 162 in the undulated region of the radially inner face 3c. These hollows 161 and bosses 162 extend one after the other longitudinally. In this case there are three hollows 161 and two bosses 162.

(73) Each hollow 161 and each boss 162 includes a curvature which extends both in the tangential direction Z and in the longitudinal direction Y.

(74) The three bosses 162 are laid out in line with the three inter-cavity partitions 44 including an axial surface forming the bottom 41 of the recessed pocket 4′ represented in FIG. 5 and the two hollows 161 are facing the two so-called central cooling channels 43 emerging radially in the bottom 41 of the recessed pocket.

(75) In this example, the radially inner face 3c further includes, on either side of the undulated region, a concave surface 31c′ having a concave radius along the transversal direction like the concave surface 31 of the first embodiment. The concave surface 31c′ extends along the undulated region and thus includes a portion of cylinder having an axis extending longitudinally like the concave surface 31 of the first example. This concave surface 31c′ extends from the upstream longitudinal end 7c and the downstream longitudinal end.

(76) In this example, the radially inner face 3 further includes, besides two concave surfaces 31, two side convex surfaces 32c′ along the side faces 6a′ and 6b′ like the side convex surface 32′ in the example of the first embodiment.

(77) According to another example, not represented, the undulated region is surrounded by a side convex surface. In other words, the undulated region extends up to the side convex surface.

(78) In this example represented in FIGS. 4a and 4b, the radially inner face 3c further includes, between the undulated region and the upstream face, an upstream concave surface 32c7 extending from one length end p7 forming the intersection line between the upstream face 7 and the radially inner face 3c. In this example, the radially inner face 3c further includes, between the undulated region and the downstream face, a downstream concave surface extending from one length end P8 forming the intersection line between the downstream face and the radially inner face 3c.

(79) The upstream concave surface 32c7 and the downstream concave surface are laid out in line with the two other upstream and downstream cooling channels 43 and two upstream and downstream inter-cavity partitions 44 including an axial surface forming the bottom 41 of the recessed pocket 4′. Thus, this makes it possible to limit the mass of the blade.

(80) The present invention relates to in this case in these examples a rotor disc of a high pressure turbine. However, the rotor disc may also be a rotor disc of a low pressure turbine. Generally speaking, the present invention thus relates to any turbomachine rotor disc. The present invention is naturally not limited to a particular type of fastener for the mounting of the blade roots on the rotor discs. Notably the examples of the second and third embodiment may have side faces like the first example of the first embodiment to be inserted into a recessed pocket of the first example of the first embodiment. Generally speaking, the present invention applies to any blade comprising a root intended to be mounted in a recessed pocket of a rotor disc while conserving, thanks to the mounting clearance between the root of the blade and the bottom of the recessed pocket, a space for circulating cooling air.